This invention pertains to an apparatus for loading test fixtures. In particular, an apparatus for automatically loading probes into test fixtures.
Test fixtures are commonly known and are used for testing printed circuit boards to verify electrical functionality and continuity between points on circuit boards. The test fixture usually includes an array of probes which are specially seated in the fixture so that one end of the probes are oriented to contact the specifically arranged circuits of printed circuit board. The other end of the probes are arranged to make contact with the specially designed pins of a testing apparatus. Generally, the pins of a test apparatus are spaced on a grid having 0.100 inch centers.
As the traces of printed circuit boards are becoming more and more miniaturized the probes within the fixture must be oriented within the fixture at an angle. Each printed circuit board has a customized design which requires the test fixture to be mated with that printed circuit board to also have a customized design.
Past fixture loading methods were slow because single-grooved probes had to be oriented properly within a cassette or fixture. Grooved pins have been disclosed in U.S. Pat. Ser. No. 07/683,872 and such grooves seat the probe within a fixture. The groove of the probe is used to provide a narrowed diameter which seats within an extended diameter area of a fixture. Due to the need for uni-directional or single-grooved probes to be positioned correctly within the fixture to provide for the proper seating of the probe, these single-grooved probes were required to be inserted by hand. As well, the manual insertion of probes was required in past fixture loading methods in order to assure the proper loading of probes into angled holes of the fixture, especially where the angles of the holes exceed 0.200 inch deflection. Other style probes are known which include "heads" or other outboard contours which are difficult to automatically load due to interlocking which may occur between adjacent probes.
It is common for probes to be constructed of music wire and have a length of approximately 3.00 inches. The long length of these probes allowed for increased deflection and reduced angling within a fixture; in that as the distance from the gridplate or bottom of the fixture to the personality plate or top of the fixture increases, the angle at which the probe is inserted into the fixture decreases while deflection capabilities increase. Thus, the use of long 3.00 inch probes is common in order to provide test fixtures for miniaturized printed circuit boards. Due to the aforementioned constraints, many of the prior art fixture loading methods were very slow and required excessive man-hours to load the fixtures.
It is a principle object of the present invention to provide a probe loading apparatus which operates automatically.
It is another object of the present invention to allow for the loading of probes at angles of up to 12 out of perpendicular with the fixture plate surface.
It is a further object of the present invention to provide for non-grid dependent cassettes.
It is another object of the present invention to provide for loading of a fixture through the bottom plate.
It is a further object of the present invention to programmably load multiple-sized probes in a single fixture.
It is another object of the present invention to provide cassettes which may load a minimum of four (4) fixtures without replenishment.